The new X Server developed under the sponsorship of freedesktop.org is aiming at replacing XFree86. Some code will be re-used but the core will be rewritten by Keith Packard and others. The new X server features full support for transparency, and has window-level image compositing among other things. Check out the screenshots (one more added, now there are four shots).

As you can see, he is using subpixel smoothing (the colored pixels), which only really makes sense on LCD displays. Apart from that, I see only minor differences, which certainly are nice though. Particulary his "s", "c" and the small "a" look slightly better. Could just as well be a modified version of the font. Or would this be the effect of font hinting?